The invention relates to a device for releasably connecting a tool to a machine spindle, comprising a tool shank projecting on the tool, a connecting sleeve projecting on the spindle coaxially to the spindle axis and having a recess for accommodating the tool shank, and a clamping mechanism which engages in the region between tool shank and connecting sleeve and has at least one essentially radially movable clamping element, the radial movement of which can be converted, preferably in the manner of a wedge drive, into an axial clamping movement between tool shank and connecting sleeve. In this case, the connecting sleeve need not be arranged directly on the machine sleeve. It may also be arranged on an adapter piece which can be releasably connected to a machine spindle. On the other hand, the tool shank need not be arranged directly on the tool either. It may be formed by an adapter piece connected to the tool.
The task of the clamping mechanism engaging in the region between tool shank and connecting sleeve is to connect the tool to the machine spindle in a rotationally locked manner by means of the at least one radially movable clamping element. When the clamping element is actuated by means of a suitable actuating mechanism, its radial movement is converted into an axial clamping movement between tool shank and connecting sleeve. In the process, taper clamping and/or flat-face clamping occurs between the clamping faces, facing one another, of the tool shank and the connecting sleeve. Pull rods, for example, are used to actuate the clamping mechanism, these pull rods passing through the machine spindle and engaging in the tool shank and being actuated from the machine side. Furthermore, it is known to actuate the clamping elements by means of screws or plungers which can be actuated radially from outside. This type of actuation has the disadvantage that a preset orientation of the spindle is necessary in order to be able to get to the actuating screws. This disadvantage has an adverse effect in particular in the case of multi-spindle heads.
Starting therefrom, the object of the invention is to improve the known device of the type specified at the beginning to the effect that it is possible to actuate the clamping mechanism independently of the machine without a specific orientation of the spindle being necessary for this purpose.
To achieve this object, the combination of features specified in patent claim 1 are proposed. Advantageous refinements and developments of the invention follow from the dependent claims.
The solution according to the invention is based on the idea that the clamping mechanism comprises an actuating nut which is screwed onto an external thread, coaxial to the spindle axis, of the connecting sleeve and the axial movement of which, during the clamping operation, with at least one intermediate member in between, can be converted into the radial movement of the clamping element. This measure achieves the effect that the clamping mechanism can be actuated via the actuating nut irrespective of the orientation of the spindle in the circumferential direction. In this case, the intermediate member is advantageously designed as a wedge drive. In order to achieve flat-face clamping between the tool shank and the connecting sleeve, it is advantageous if the tool shank is defined at its root by a radially projecting annular surface, against which the connecting sleeve can be pressed with its free end face under the effect of the clamping mechanism.
A preferred refinement of the invention provides for at least one clamping element to be designed as a clamping bolt which is radially guided in a guide bore passing through the sleeve wall of the connecting sleeve and has a wedge surface at its end projecting outward beyond the guide bore, and for the intermediate member to be designed as an axially displaceable intermediate ring which is arranged in a non-rotatable manner on the outside of the connecting sleeve between the actuating nut and the clamping bolt and has a wedge surface bearing against and complementary to the wedge surface of the clamping bolt. In this case, the wedge surface of the clamping element and/or of the intermediate member is expediently subdivided into a steeper adjusting bevel and a flatter clamping bevel with regard to the displacement direction of the intermediate member. The wedge surfaces of the intermediate ring may be defined by two lateral guide surfaces which face one another in the circumferential direction, are oriented in an axially parallel manner, laterally overlap the projecting end of the clamping bolt and in the process form an anti-rotation locking means for the intermediate member, the intermediate ring expediently being axially guided on the outer surface of the connecting sleeve outside the wedge surfaces defined by the lateral guide surfaces. An axial supporting bearing designed as a plain or rolling-contact bearing may be arranged in the abutting region between the actuating nut and the intermediate ring. This facilitates the axial displacement of the intermediate ring by the actuating nut. Furthermore, the actuating nut may carry an annular extension piece which axially overlaps the intermediate ring on the outside and may be integrally formed in one piece on the actuating nut or connected to the latter as a separate part, in particular screwed, adhesively bonded, brazed on or shrunk on. In order to facilitate the detaching operation, it is advantageous if the annular extension piece has a driver engaging behind the intermediate ring at an annular shoulder remote from the actuating nut. The risk of contamination from outside is reduced if an annular cap projecting radially beyond the connecting sleeve and fixed to the latter is arranged on that side of the guide bores which is axially opposite the actuating nut. In this case, the annular extension piece of the actuating nut may axially overlap the annular cap at its circumferential surface. A further improvement in this respect can be achieved if a radially acting sealing ring is arranged between annular cap and annular extension piece. In order to achieve antirotation locking of the clamping bolt in the guide bores, it is advantageous if the clamping bolt, on its guide surface opposite the wedge surface, has a radially oriented guide groove in which a guide pin projecting beyond the annular cap engages in an axially parallel manner.
In a further preferred refinement of the invention, the clamping bolt has a tapered extension bearing against an internal taper on the tool-shank side. In addition, the tool shank may have a transverse bore in which at least one floating bolt having an internal taper is arranged in a displaceable manner. In order to achieve flat-face clamping, it is advantageous if the internal taper on the tool-shank side and the tapered extension on the clamping-bolt side are offset axially in the clamping direction during the clamping operation. In a preferred refinement of this embodiment variant, the clamping mechanism has two clamping bolts which are of identical design, are radially guided in diametrically opposite guide bores of the connecting sleeve, are displaceable by the actuating nut via the intermediate ring provided with two diametrically opposite wedge surfaces and each engage by means of their inwardly pointing tapered extension in a respective end internal taper of the floating bolt.
A further advantageous embodiment variant of the invention provides for the at least one clamping element to be designed as a clamping claw which, at its one end, has an anchor part, which can be supported on an inner shoulder of the connecting sleeve, and, at its other end, has a claw part which reaches into a cavity of the tool shank and can be pivoted there into an inner recess, the claw part and the boundary wall of the inner recess having wedge surfaces which are complementary to one another and via which the radial movement of the claw part can be converted into an axial clamping movement between tool shank and connecting sleeve. In this case, the intermediate member is designed as a plunger which is arranged in a non-rotatable manner in the interior of the connecting sleeve and the tool shank, has a complementary wedge surface bearing against an inner wedge surface of the clamping claw and is axially displaceable indirectly via the actuating nut between a release position and a clamping position. In this arrangement, the actuating nut is expediently coupled to the plunger via a transverse bolt which passes through at least one elongated hole, oriented in an axially parallel manner, of the connecting sleeve, in which case the transverse bolt can pass through an elongated hole, oriented in an essentially axially parallel manner, in the clamping element. At least two clamping elements of said type arranged in the circumferential direction at equal angular distances from one another and designed as clamping claws are advantageously provided. In addition, the plunger may at the same time be designed as an ejector which is effective during the release operation and which for this purpose may have an ejector head bearing against an inner surface of the tool shank.
A preferred refinement of the invention provides for the transverse bolt to be mounted with its ends in a thrust ring which is guided in a non-rotatable manner on the connecting sleeve and in such a way as to be axially displaceable via the actuating nut. The thrust ring may have two diametrically opposite recesses for accommodating the transverse-bolt ends, in which case the thrust ring, which overlaps the transverse-bolt ends on the outside, can be connected in each case via a radial pin to the transverse-bolt ends.
A further advantageous refinement of the invention provides for the actuating nut to have an annular extension which axially overlaps the thrust ring and which, on that side of the transverse bolt which is axially opposite the actuating nut, can be rigidly connected to a pull ring driving the transverse bolt in the release direction. A supporting bearing designed as an axial plain or rolling-contact bearing can be arranged both between the actuating nut and the thrust ring and between the pull ring and the thrust ring.
A particular solution variant of the invention provides for the thrust ring to have a thread interacting with a thread of the actuating nut and coaxial to the actuating nut. The thrust ring expediently has an external thread interacting with an internal thread of the actuating nut. In this case, the thrust ring and a pull ring arranged on that side of the transverse bolt which is axially opposite the actuating nut may be rigidly connected to one another.
It is also advantageous in this embodiment variant that the wedge surface of the plunger and/or the associated wedge surface of the clamping claw has a steeper adjusting bevel and a flatter clamping bevel with regard to the displacement direction of the intermediate member.
A preferred refinement of the invention provides for the clamping claws to be arranged with axial clearance in a centering cage which has two pistons which are connected to one another by webs and each engage in a respective cylindrical recess of the tool shank and the connecting sleeve. In this case, the webs may be designed as coolant tubes which pass through the pistons and to which cooling lubricant can be admitted.